Figure 3.1 Standard curve shapes for inverse time over-current, with time multiplier setting (TMS) = 1
0.1
1
10
100
1000
1 10 100
G / Gs
time
[s]
IEC Inverse
IEEE Moderately inverse
IEC Very inverse
IEEE Very inverse
IEC Extremely inverse
IEEE Extremely inverse
Definite time characteristic
G
D
is the point where the alarm shifts from an inverse curve to a definite time characteristic, as the following graph shows. That is,
after this point, the curve is flat, and a current increase does not have any effect on the alarm response time. In IEC60255, this point
is defined as G
D
= 20 × G
S
.
DESIGNER'S HANDBOOK 4189340911K UK Page 71 of 521
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